Antennas formed from flat coils representing a large number of superimposed turns are known. The electromagnetic field generated by these antennas is, on their surface or near their surface, substantially perpendicular to this surface. Since electronic tags, such as transponders or RFID (Radio Frequency Identification) tags can only be read if the surface of their antenna cuts a sufficient number of field lines, they cannot be read when the plane of their antenna is oriented substantially perpendicular to the plane of the read antenna.
Antennas arranged around a volume, for example on the sides of a box through which tags pass to be read, are also known. These boxes are bulky and cannot be used for the passage of large objects.
Lastly, figure-8 shaped antennas display the following disadvantages:                the field is high in the immediate neighborhood of the central wires but decreases quickly on moving away;        the antenna inductance may be relatively high since all the turns are identical resulting in bulky strands around the structure (300 to 400 pH for an antenna of 30 cm by 40 cm)        these antennas are poorly adapted to reading stacks of RFID tags (a few dozen for example).        